Method and apparatus for transferring movable coils of a variable induction device

ABSTRACT

A method and apparatus for transferring the turns and windings of a movable coil between two drum portions, such as either from one drum to another or from one position on a drum to another postion thereon, in response to the rotation of the drum portions. The coil includes an intermediate portion extending between the drum portions and resilient guide means is provided to guide the coil as it is transferred and to allow the intermediate portion to vary slightly in length during the transfer of the coil so that the intermediate portion is not subject to excessive slack and stress. In addition, a drive means if provided to rotate the drum portions in synchronism when the drum portions comprise, for example, two independently mounted drums.

[ Dec. 25, 1973 United States Patent [191 Rozelle METHOD AND APPARATUS FOR TRANSFERRING MOVABLE COILS OF A imary Examiner-Ge0rge F. Mautz VARIABLE INDUCTION DEVICE Assistant Examiner-Edward J. McCarthy Attorney-Robert S. Swecker [75] Inventor: Donald S. Rozelle, Owego, NY.

[73] Assignee: Magnetech Industries, Inc., Newark Valley, NJ.

[ Filed: 1972 A method and apparatus for transferring the turns and [21] 1 ;219 39 windings of a movable coil between two drum portions, such as either from one drum to another or from one position on a drum to another postion thereon, in response to the rotation of the drum portions. The coil includes an intermediate portion extending between the drum portions and resilient guide means is provided to guide the coil as it is transferred and to allow 82 Bmm 1 32H 3. $1 2 4 1 2 2 4 4 2 m l l". 6 U 3 U" mTm m... 6 WW I. C WM 1.0 I ll U.mF 1.1] 18 555 [.11

the intermediate portion to vary slightly in length during the transfer of the coil so that the intermediate [56] References Cited UNITED STATES PATENTS portion is not subject to excessive slack and stress. In

1,668,414 5/1928 Martin 3,614,692 10/1971 Rozelle 2,731,605 1/1956 Doelz FOREIGN PATENTS OR APPLICATIONS 1 1 833,792 4/1960 Great Britain....................... 33811.9 3 C 3 Drawmg F'gures 1 METHOD AND APPARATUS FOR TRANSFERRING MOVABLE COILS OF A VARIABLE INDUCTION DEVICE BACKGROUND OF 'THE INVENTION The present invention relates to variable induction devices and more specifically to a method and apparatus for transferring moveable inductor coils of a variable induction device to vary the effective number of turns of the coils.

Among the more common types of variable induction devices such as transformers are the conventional autotransformer and transformers utilizing tap changing systems. The autotransformer is similar to a potentiometer in that a variable output voltage is picked off a transformer winding by a sliding contact. The use of a tap changing system to provide a variable output voltage requires the selective making and breaking of contacts connected at desired points along a transformer winding. Both types of variable transformers are subject to mechanical wear and do not provide a truly continuous output voltage, i.e., the output voltage varies incrementally with these types of systems.

In another type of variable induction device disclosed and claimed in U. S. Rozelle et al. Pat. No. 3,614,692, assigned to the assignee of the present invention, a highly accurate, continuously variable output voltage may be provided particularly when utilized in conjunction with the coupling arrangement disclosed and claimed in U. S. Pat. application Ser. No. 171,206 now Patent No. 3,732,487 by Donald S. Rozelle and assigned to the assignee of the present invention. Briefly, a moveable coil, the turns of which are transferrable between two spaced rotatably mounted drums, is linked by a cyclically varying magnetic flux from a primary transformer winding and an output voltage is generated across the moveable coil. The effective number of turns and therefore the output voltage of the movable coil may be varied by rotating the drums.

- To accomplish the transfer of coil turns from one drum to the other, the drums are preferably rotated in synchronism so that as the numbers of turns on one drum decreases, the number of turns on the other drum increasesin a direct relation. The synchronous drive of the two drums may, of course, be achieved through the use of direct gear drives. However, this may require the use of precisely machined. gears which may, through frequent use, become worn and provide sloppy control of drum rotation. Should this happen, excessive stress may be placed on the portion of the transferrable coil intermediate to the drums.

Under ideal circumstances when the two drums are rotated in synchronism, the portion of the transferrable coil intermediate the drums will remain constant in length and under a constant tension. Such ideal conditions include, for example, exact correspondence between drum diameters throughout the lengths thereof and a constant diameter of the conductor utilized for the moveable coil throughout the lengthof this conductor. It may, however, be impractical to attempt to obtain such ideal drum and conductor dimensions.

For example, the drums may be molded from a resinous material and drum diameter may vary in proportion to the amount of filler material used and the purity of the resin since the shrinkage of the cured material may vary in proportion to these factors. Without further machining, drum diameters may thus vary slightly from one batch of drums to the next. In a device such as the variable induction device described in the references Rozelle et al. patent application, particularly where interchangeable drums are utilized, slight differences in drum diameter due to differences in shrinkage of the resins or other factors may be quite important.

Assuming, for example, that the mold diameter from which the drums are made is 3 inches and no shrinkage occurs when manufacturing one of the drums, the circumference of the drum would be about 9.42 inches. Assuming that a second drum made from the same mold has a shrinkage of 0.005 inches in diameter, the circumference of the second drum would be approximately 9.414 inches. A difference. of 0.016 inches would be present between the circumferences of the two drums. Assuming that the total number of turns of the transferrable coil is 40, this 0.016 inch difference in drum circumferences represents a difference of 0.64 inches in required total conductor length between the two drums. Thus, the conductor length required when all turns are wound on to the larger diameter drum is about 0.64 inches greater than when all of the turns are wound on the smaller drum.

If, under these conditions, all of the turns are initially wound on the larger drum and then transferred to the smaller drum, the intermediate portion of the conductor will have about 0.64 inches of slack in it after all of the turns are transferred. On the other hand, if all of the turns of the moveable coil are initially wound on the smaller of the drums and then all transferred to the larger of the drums, the coil will necessarily be stretched about 0.64 inches in length by the time all of the coils are transferred from the smaller to the larger drum.

It is apparent that under such circumstances as in the above example, the conditions resulting inthe slackening of the intermediate portion of the transferrable coil may result in the overwinding or other undersirable transfer of the coil. Under the condition where more conductor length is required as when the coil is transferred from the smaller drum to the larger drum, the conductor length must increase and therefore is placed under considerable stress causing stretching and perhaps even breaking of the conductor.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to obviate these and other problems associated with the synchronous transfer of turns of a coil from a position on a drum to another position on the same drum or to another drum.

It is another object of the present invention to provide a novel apparatus for compensating for differences in required conductor length during transfer of turns of the coil from one position to another.

It is yet another object of the present invention to provide a novel method and apparatus for synchronously rotating two drums with a minimum of space requirements and while minimizing the required accuracy of the intermeshing parts.

These and other objects and advantages are accomplished in accordance with the present invention by a preferred embodiment in which the turns or windings of a coil are adapted to be transferred between two drum portions, such as from either one drum to another or from one position on a drum to another position thereon, in response to the rotation of the drum portions. TI-Ie coil includes an intermediate portion extending between the drum portions and resilient means is provided to allow the intermediate portion to vary slightly in length during the transfer of the coil so that the intermediate portion is not subject to excessive slack and stress. In addition, a drive means is provided to rotate the drum portion in synchronism when the drum portions comprise, for example, two independently mounted drums.

THE DRAWINGS This preferred embodiment is illustrated in the accompanying drawings in which:

FIG. 1 is a perspective view of a variable induction device incorporating the conductor transport mechanism in accordance with the present invention;

FIG. 2 is a cross sectional view of the variable induction device along the line 22 inFIG. 1; and

FIG. 3 isa cross sectional view of the variable induction device along the line 3-3 in FIG. 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Referring to FIG. 1, the variable induction device of the present invention preferably comprises a rectangular laminated core having a removeable end member 12, two generally cylindrical substantially hollow drums 14A and 14B carried by opposite legs of the core 10 for axial rotation about the longitudinal axes thereof, an electrically conductive coil 16 having two portions 16A and 168 formed by and connected by a flexible conductor 18 wound about each of the drums 14, a .synchronous drum drive means generally indicated at 20, and'a conductor transport means generally indicated at 22.

The drums 14A and 14B may be mounted for axial rotation on two cylindrical members (not shown) which may be non-rotatably carried'by opposite lengths of core 10 in telescoping rotation therewith. A primary transformer winding (not shown) may be carried by each of the cylindrical members to provide a means for inducing a cyclically varying magnetic flux which links the coils 16 to generate an output'voltage. This output voltage may'be provided at stationary output terminals through the use of brush and ring arrangements preferably of the type disclosed and claimed in the previously referenced Rozelle Patent application Ser. No. 17 l ,206 or of the type disclosed and claimed in U. S. Pat. application Ser. No. l56,3l l by Donald S. Rozelle et al. The disclosures of these applications is hereby incorporated herein by reference. Moreover, a more detailed description of the drums 14, the cylindrical members and the various transformer windings which may be provided beneath the drums 14 may be had by reference to the previously mentioned Rozelle et al. Pat. No. 3,6 I 4,692, the disclosure of which is also hereby incorporated herein by reference.

With continued reference to FIG. 1 and with reference to FIG. 2, the drive means 20 preferably comprises a drive gear 24 having teeth 26 disposed circumferentially therearound, circumferential flanges 28 and 30 at adjacent ends of the respective drums 14A and 14B and having gear teeth 32 and 34 circumferentially therearound, and an endless belt such as a timing belt having interiorly disposed teeth which positively mesh with the teeth 26, 32 and 34 of the drive'gear 24, the flange 28 and the flange 30, respectively.

The drive gear 24 may be mounted adjacent the flanges 28 and 30 on one end of a drive shaft 38, and the drive shaft 38 may be journalled for rotation at each end thereof in a pair of end brackets 40 and 42 connected to and extending upwardly from the end members 12 and 12 of the core 10. The drive shaft'is preferably threaded along its entire length to correlate the movement of the conductor transport means 22 with the rotating of the drums as will hereinafter be described in detail. A crank handle 44 or other suitable means may be connected to the shaft 38 to drive the gear 24 through the drive shaft 38.

The flanges 28 and 30 and the gear teeth 32 and 34 associated therewith may be an integral part of the respective drums 14A and 14B, the drums, flanges and teeth being, for example, molded in a single operation. The dimensions of the gear teeth 32 and 34 are substantially the same as those of the teeth 26 of the drive gear 24 although it should be noted that the use of a belt such as the timing belt 36 permits some slight variations without danger of binding and the like. The number of teeth 32 and 34 on the respective flanges 28 and 30 is identical to provide the desired synchronous rota tion of the drums. I

A guide rod 46 is mounted generally parallel to and spaced from the shaft 38. For example, the ends of the guide rod 46 may slidably pass through holes in the end brackets 40' and 42 and may be secured against removal by suitable conventional self binding fasteners such as cap nuts 48 (only one shown). Alternatively, the guide rod receiving hole in one of the end brackets may be threaded to securely receive the corresponding end of the guide rod 46 with the other end of the guide rod 46 secured by a suitable fastener as described above.

With continued reference to FIGS. 1 and 2, it can be seen that the drive gear 24 is disposed intermediate the drums 14A and 14B and is displaced upwardly from a plane containing the axes of the drums 14A and 143. By way of further explanation, lines indicated at 50A, 50B and 50C connecting the axes of the drums 14A and 14B to each other and to the axis of the drive gear 24 form a triangle, the sides 50B and 50C of which are generally equal in length. THe drive gear 24 may be smaller in diameter'than the diameters of the flanges 28 and 30 on the drums 14A and 143, respectively and may be provided with fewer gear teeth 26 than the flanges 28 and 30 so that, for example, two revolutions of the drive gear 24 effects one revolution of each of the drums 14A and 148. The relatively small diameter of the drive gear 24 permits a relatively small, compact drive unit since the distance represented by the sides 50B and 50C may be less than the distance represented by side 50A.

However, this relatively small size of the drive gear 24 and its relatively close spacing to the flanges 28 and 30 of the respective drums 14A and 14B may, for example, cause only about one third of the teeth 26 of the drive gear 24 to mesh with the teeth of the timing belt 36. With this type of three-point drive, slippage of the drive belt 36 may result unless an external tensioning device is utilized to maintain the necessary belt tension. It may be necessary, in fact, to use a spring loaded tension compensator since belt length may vary with wear and other conditions. v

This need for external tension compensators is eliminated according to the present invention by positioning the elongated guide rod 46 at a distance D (FIG. 2)

from the top of the belt 36 when the belt 36 is in proper and tight engagement with the teeth 26 of the drive gear 24. The distance D is less than the depth of the teeth of the belt 36 and the belt 36 is thus prevented from rising out of engagement with the teeth 26 of the gear 24. Should the belt 36 rise and contact the guide rod 46 when the belt is moving, the guide rod will thus prevent the belt 36 from not advancing with rotation of the drive gear 24.

Any variationsin the length of the belt 36 which tend to cause belt 36 to rise out of engagement with the teeth of the drive gear 24 thus do not result in belt slippage or binding. This is particularly important in that lost motion of the drive gear 24 may result in a loss of coincidence between the position of the coil portions 16A and 16B on the drums 14A and 14B with respect to the conductor transport mechanism 22 hereinafter described in greater detail. Moreover, it is not critical that a predetermined belt tension be established and maintained.

With reference to FIGS. 1 and 3, the conductor transport means 22 cooperate with the threaded drive shaft 38 to correlate the transfer of the moveable coil 16 with drum rotation. The transport means 22 preferably includes a conductor guide means 52 having a threaded aperture 54 and a guide rod receiving aperture 56 therethrough. As is shown in FIG. 1, the threaded drive shaft 38 passes through the threaded aperture 54 in the guide means 52 so that rotation of the shaft 38 causes movement of the guide means 52 along the length of the shaft 38. The guide rod 46 passes slidably through the aperture 56 in the guide means 52 so that the guide means 52 may slide along the guide rod 46 as the shaft 38 is rotated. The guide rod 46 is thus operable both to prevent the guide means 52 from ro- ,tating out of its illustrated upright position and to prevent the belt 36 from moving out of engagement with the drive gear 24.

The guide means 52 is provided with a slot 58 or other suitable conductor guiding means through which the portion of the conductor 18 intermediate the drums 14A and 14B may slidably pass.- In the preferred embodiment, the portion of the conductor 18 intermediate the drums 14A and 14B passes through the slot 58 and is biased upwardly along an arcuate path between the drums 14A and 14B by resilient means generally indicated at 60.

The resilient means 60 may include, for example, two cylindrical coil springs 62 each received in a hole 64 disposed generally transversely to the slot 58. Each spring 62 may be adjustably secured against removal by set screws 66 or other suitable securing means. Nylon balls 68 or other suitable smooth or generally rounded members may be provided intermediate the springs 62 and the conductor 18 to provide smooth bearing surfaces against which the conductor 18 may ride as it passes through the slot 58.

As is apparent from F 1G. 1, the slot 58 is sufficiently wide to permit the conductor 18 to pass therethrough without binding while providing a guide for the conductor 18 which moves along the length of the drums in correspondence with drum rotation as the turns of the coil 16 are transferred from one drum to the other. The

depth of the slot, i.e., the dimension of the slot in a direction perpendicular to the plane containing the axes of the drums, is sufficient to permit the maximum anticipated upward and downward movement of the intermediate portion of the conductor 18 due to lengthening and shortening of the intermediate portion along its arcuate path resulting from differences in drum diameter and the like. In this manner, compensation is provided for variations in the length of the portion of the conductor 18 intermediate the drums 14A and 148 through compression of the springs 62. Thus, a fairly even pressure is applied to that portion of the conductor 18 intermediate the drums 14A and 14B as the length of this intermediate portion varies.

From the foregoing, it is apparent that a highly desirable wire lay may be achieved utilizing the present invention. For example, a drive gear 24 having 24 teeth used in conjunction with drums each having 48 teeth provides one revolution of the drums for every two revolutions of the drive gear. When utilizing a threaded shaft 38 having 28 threads per inch and a conductor 18 having a diameter of 0.071 inches, the two revolutions of the shaft 38 result in a 0.071 inch movement of the guide means, this movement being equal to the conductor diameter. This results in the desired wire lay on the .drums with any slight variations being compensated for by the resiliency of the guide means.

While the present invention has been described in connection with a preferred embodiment, the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. For example, in connection with the conductor transport means of the present invention, the conductor may be transferred through the use of the conductor transport means for one position on one portion of a drum and wound onto another portion of the same drum in another position, rather than being transferred between two separate, independently mounted drums. The presently disclosed embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to beembraced therein.

What is claimed is:

1. Apparatus comprising:

first and second drum portions mounted for axial rotation about a magnetic core; electrically conductive coil means wound on both of said drum portions and adapted to be selectively transferred from one of said drum portions to the other in response to the rotation of said drum portions, said coil means including an intermediate portion extending between the drum portions along a substantially arcuate path; and,

resilient means moveable longitudinally with respect to said drum portions in response to the rotation thereof and engaging said intermediate portion for applying a substantially constant pressure to said intermediate portion irrespective of slight variations in the length of said intermediate portion as said coil means is transferred from one drum portion to the other.

2. The apparatus of claim 1 wherein said resilient means comprises:

a generally upright member having a threaded aperture therethrough,

a threaded shaft passing through said threaded aperture in threaded engagement therewith;

said upright member including means slidably engaging said intermediate portion of said coil means for guiding said coil means from a position along one of said drum portions to a position along the other of said drum portions; and,

means carried by said upright member for resiliently biasing said intermediate portion of said coil means outwardly away from said drum portions.

3. The apparatus of claim 1 wherein said drum portions are independently mounted for axial rotation on opposite parallel legs of said magnetic core and including means for synchronously rotating said drum portions.

4. The apparatus of claim 3 wherein said rotating means comprises:

drive means, including a threaded shaft disposed generally parallel to the axes of said drums, for rotating said drums in synchronism;

said resilient means being mounted on said threaded shaft for movement along said threaded shaft in response to the rotation thereof.

5. The apparatus of claim 4 wherein said drive means includes: I l

drive gear means connected one end thereof; first and second gear means each connected to anassociated one of said drum portions substantially coplanarly with said drive gear means,

an endless belt having teeth disposed interiorly thereof,

said belt being disposed in circumscribing relation with said drive gear means and said first and second gear means whereby said teeth engage all of said gear means; and

an elongated guide rod spaced from and generally parallel to said threaded shaft,

said resilient means slidably engaging said guide rod to prevent rotation of said guide means and said guide rod cooperating with said belt to prevent disengagement ofsaid teeth from said drive gear means;

6. The apparatus of claim 3 wherein said rotating means comprises: I v

first and second substantially identical gear means connected, respectively, to said first and second drum portions and disposed coaxially with respect thereto, said gear means being disposed at adjacent ends of said drum portions with said drum portions mounted on said opposite legs;

driving gear means generally coplanar with said gear means and disposed generally equidistantly from said gear means;

endless belt means having gear teeth disposed interiorly thereof and positioned in circumscribing relation to said gear means and said driving gear means, said gear teeth positively engaging said gear means and said driving gear means;

means for rotating said driving gear means to thereby rotate said drum portions in synchronism; and means cooperable with said driving gear means for preventing the disengagement of said teeth of said belt means from said driving gear means.

7. The apparatus of claim 1 wherein said resilient means comprises:

guide means movable generally parallel to the axes of said drum portions in response to the rotation of said drum portions for guiding said coil means from to, said threaded shaft at a position along one of said drum portions to a desired position along the other of said drum portions; and

means carried by said guide means for resiliently biasing a portion of said coil means intermediate said drum portions outwardly away from said drum portion along a substantially arcuate path.

8. in a variable induction device including a pair of spaced, axially rotatable drums having electrically conductive coil means wound on the drums and adapted to be transferred from one drum to the other responsively to the rotation of the drums, the improvement comprising:

guide means movable generally parallel to the axes of said drums in response to the rotation of said drums for aligning said coil means on said drums during the transfer of said coil means from one drum to the other; and

means carried by said guide means and engaging a portion of said coil means intermediate said drums for resiliently biasing said portion of said coil means outwardly away from said drums along a substantially arcuate path between the drums,said

v biasing means permitting said intermediate portion to vary .in length while maintaining a substantially even stress on said intermediate portion whereby excessive stress and excessive slackening of said intermediate portion is prevented.

9. The variable induction device of claim 8 comprising:

drive means, including a threaded shaft disposed generally parallel to the axes of said drums, for rotating said drums in synchronism; and,

said guide means. being mounted on said threaded shaft for movement along said threaded shaft in response to the rotation thereof.

10. The variable induction device of claim 9 including;

an elongated guide rod spacedfrom'and generally parallel to said threaded shaft,

said guide rod being slidably engaged by said guide means'so that said guide means is secured against rotation.

11. The variable induction device of claim 9 wherein said drive means includes:

drive gear means connected to said threaded shaft at one end thereof;

first and second gear means each connected to an associated one of said drums substantially coplanarly with said drive gear means;

an endless belt having teeth disposed interiorly thereof,

said belt being disposed in circumscribing relation with said drive gear means and said first and second gear means whereby said teeth engage all of said gear means; and

an elongated guide rod spaced from and generally parallel to said threaded shaft,

said guide means slidably engaging said guide rod to prevent rotation of said guide means and said guide rod cooperating with said belt to prevent disengagement of said teeth from said drive gear means.

12. The variable induction device of claim 9 wherein said guide means comprises:

a generally upright member having a threaded aperture therethrough,

said threaded shaft passing through said threaded aperture in threaded engagement therewith;

said upright member including means slidably engaging said portion of said coil means intermediate said drums for guiding said coil means from a position along one of said drums to a position along the other of said drums;

said means for resiliently biasing being carried by said upright member.

13. A method for transferring electrically conductive coil means from one drum portion to another drum portion in a variable induction device including two drum portions mounted for axial rotation about a magnetic core and electrically conductive coil means transferable between said drum portions in response to the rotation thereof, the method comprising the steps of:

slidably engaging a portion of the coil means intermediate the drum portions with a guide means disposed intermediate the drum portions;

rotating the drum portions in synchronism;

moving the guide means generally parallel to the axes of the drum portions in response to the rotation of the drum portions to thereby guide the coil means from a position along one of the drum portions to a position along the other of the drum portions; and

resiliently biasing the slidably engaged portion of the coil means intermediate the drum portions outwardly away from the drum portions and along a substantially arcuate path between the drum portions to thereby permit the intermediate portion to vary in length while maintaining a substantially even stress on the intermediate portion. 

1. Apparatus comprising: first and second drum portions mounted for axial rotation about a magnetic core; electrically conductive coil means wound on both of said drum portions and adapted to be selectively transferred from one of said drum portions to the other in response to the rotation of said drum portions, said coil means including an intermediate portion extending between the drum portions along a substantially arcuate path; and, resilient means moveable longitudinally with respect to said drum portions in response to the rotation thereof and engaging said intermediate portion for applying a substantially constant pressure to said intermediate portion irrespective of slight variations in the length of said intermediate portion as said coil means is transferred from one drum portion to the other.
 2. The apparatus of claim 1 wherein said resilient means comprises: a generally upright member having a threaded aperture therethrough, a threaded shaft passing through said threaded aperture in threaded engagement therewith; said upright member including means slidably engaging said intermediate portion of said coil means for guiding said coil means from a position along one of said drum portions to a position along the other of said drum portions; and, means carried by said upright member for resiliently biasing said intermediate portion of said coil means outwardly away from said drum portions.
 3. The apparatus of claim 1 wherein said drum portions are independently mounted for axial rotation on opposite parallel legs of said magnetic core and including means for synchronously rotating said drum portions.
 4. The apparatus of claim 3 wherein said rotating means comprises: drive means, including a threaded shaft disposed generally parallel to the axes of said drums, for rotating said drums in synchronism; said resilient means being mounted on said threaded shaft for movement along said threaded shaft in response to the rotation thereof.
 5. The apparatus of claim 4 wherein said drive means includes: drive gear means connected to said threaded shaft at one end thereof; first and second gear means each connected to an associated one of said drum portions substantially coplanarly with said drive gear means, an endless belt having teeth disposed interiorly thereof, said belt being disposed in circumscribing relation with said drive gear means and said first and second gear means whereby said teeth engage all of said gear means; and an elongated guide rod spaced from and generally parallel to said threaded shaft, said resilient means slidably engaging said guide rod to prevent rotation of said guide means and said guide rod cooperating with said belt to prevent disengagement of said teeth from said drive gear means.
 6. The apparatus of claim 3 wherein said rotating means comprises: first and second substantially identical gear means connected, respectively, to said first and second drum portions and disposed coaxially with respect thereto, said gear means being disposed at adjacent ends of said drum portions with said drum portions mounted on said opposite legs; driving gear means generally coplanar with said gear means and disposed generally equidistantly from said gear means; endless belt means having gear teeth disposed interiorly thereof and positioned in circumscribing reLation to said gear means and said driving gear means, said gear teeth positively engaging said gear means and said driving gear means; means for rotating said driving gear means to thereby rotate said drum portions in synchronism; and means cooperable with said driving gear means for preventing the disengagement of said teeth of said belt means from said driving gear means.
 7. The apparatus of claim 1 wherein said resilient means comprises: guide means movable generally parallel to the axes of said drum portions in response to the rotation of said drum portions for guiding said coil means from a position along one of said drum portions to a desired position along the other of said drum portions; and means carried by said guide means for resiliently biasing a portion of said coil means intermediate said drum portions outwardly away from said drum portion along a substantially arcuate path.
 8. In a variable induction device including a pair of spaced, axially rotatable drums having electrically conductive coil means wound on the drums and adapted to be transferred from one drum to the other responsively to the rotation of the drums, the improvement comprising: guide means movable generally parallel to the axes of said drums in response to the rotation of said drums for aligning said coil means on said drums during the transfer of said coil means from one drum to the other; and means carried by said guide means and engaging a portion of said coil means intermediate said drums for resiliently biasing said portion of said coil means outwardly away from said drums along a substantially arcuate path between the drums, said biasing means permitting said intermediate portion to vary in length while maintaining a substantially even stress on said intermediate portion whereby excessive stress and excessive slackening of said intermediate portion is prevented.
 9. The variable induction device of claim 8 comprising: drive means, including a threaded shaft disposed generally parallel to the axes of said drums, for rotating said drums in synchronism; and, said guide means being mounted on said threaded shaft for movement along said threaded shaft in response to the rotation thereof.
 10. The variable induction device of claim 9 including: an elongated guide rod spaced from and generally parallel to said threaded shaft, said guide rod being slidably engaged by said guide means so that said guide means is secured against rotation.
 11. The variable induction device of claim 9 wherein said drive means includes: drive gear means connected to said threaded shaft at one end thereof; first and second gear means each connected to an associated one of said drums substantially coplanarly with said drive gear means; an endless belt having teeth disposed interiorly thereof, said belt being disposed in circumscribing relation with said drive gear means and said first and second gear means whereby said teeth engage all of said gear means; and an elongated guide rod spaced from and generally parallel to said threaded shaft, said guide means slidably engaging said guide rod to prevent rotation of said guide means and said guide rod cooperating with said belt to prevent disengagement of said teeth from said drive gear means.
 12. The variable induction device of claim 9 wherein said guide means comprises: a generally upright member having a threaded aperture therethrough, said threaded shaft passing through said threaded aperture in threaded engagement therewith; said upright member including means slidably engaging said portion of said coil means intermediate said drums for guiding said coil means from a position along one of said drums to a position along the other of said drums; said means for resiliently biasing being carried by said upright member.
 13. A method for transferring electrically conductive coil means from one drum portion to another drum portion in a variabLe induction device including two drum portions mounted for axial rotation about a magnetic core and electrically conductive coil means transferable between said drum portions in response to the rotation thereof, the method comprising the steps of: slidably engaging a portion of the coil means intermediate the drum portions with a guide means disposed intermediate the drum portions; rotating the drum portions in synchronism; moving the guide means generally parallel to the axes of the drum portions in response to the rotation of the drum portions to thereby guide the coil means from a position along one of the drum portions to a position along the other of the drum portions; and resiliently biasing the slidably engaged portion of the coil means intermediate the drum portions outwardly away from the drum portions and along a substantially arcuate path between the drum portions to thereby permit the intermediate portion to vary in length while maintaining a substantially even stress on the intermediate portion. 